The initial formation of the interface in the metal/compound-semiconductor system

了解金属/半导体系统中界面的形成过程和原子结构对改进其技术具有重要意义。因此，尽管这种界面已经被广泛研究了几十年，但很少有与金属/化合物-半导体系统相关的工作被开展。在这项工作中，我们报告了Sn/InSb (111) A-2x2体系中界面形成的初始阶段的扫描隧道显微镜（STM）研究。到目前为止，该系统一直是RHEED研究和DV-X alpha计算的主题。然而，“Sn吸附在InSb (111) A-2x2表面的哪里？”的问题无法通过STM等直接方法得到回答。通过在460℃附近的狭窄温度范围内退火，可以在特高压条件下制备出干净、轮廓清晰的InSb (111) a -2x2衬底表面。InSb (111) A-2x2表面的STM观测揭示了Bohr等人已经报道的空位屈曲结构。例如，占位态的STM表现在高偏压下靠近in空位的第二层Sb的孤对和低偏压下in的最外层与Sb的第二层之间的成键轨道。偶尔会观察到边缘垂直于8[112]或[112]方向的双层台阶。在电子计数模型的基础上，提出了一种新的阶梯结构模型。Sn在InSb (111) A-2x2表面的以下三个位置非周期性吸附；in -vacancy的顶部位置，Sb在第二层，in在最外层。在这些吸附位点中，空位顶部最容易被Sn占据。

Understanding of the formation process and atomic structure of interfaces in the metal/semiconductor system is very important for improvements in its technology. Therefore, although such interfaces have been studied extensively for decades, little work associated with the metal/compound-semiconductor system has been carried out.In this work we report on the scanning tunneling microscopy (STM) study of the very initial stage of the interface formation in the Sn/InSb (111) A-2x2 system. So far this system has been the subject of RHEED investigation and DV-X alpha calculation. However, the question on "where is the Sn adsorbed on the InSb (111) A-2x2 surface? " has not been answered by direct methods such as STM.The clean and well-defined substrate surface of InSb (111) A-2x2 could be reproducibly prepared in UHV by annealing a sample in the narrow range near 460ﾟC.STM observations of the InSb (111) A-2x2 surface reveal the In-vacancy buckling structure which has been already reported by Bohr et al. For example, the STM for the occupied states manifests itself in the images corresponding to the lone-pair of Sb in the second layr near the In-vacancy at a high bias and to the bonding orbitals between the outermost layr of In and the second layr of Sb at a low bias. Occasionally, bilayr steps, the edges of which are perpendicular to eht [112] or [112] direction were observed. A novel model of these step structures is proposed on the basis of the electron counting model. The Sn is non-periodically adsorbed on the following three sites of the InSb (111) A-2x2 surface ; on-top sites of the In-vacancy, of the Sb in the second layr, and of the In in the outermost layr. Of these adsorption sites, the on-top of In-vacancy is most favorably occupied by Sn.